Electrical resistance instrument



Nov. 2 1926.

- F. c. KRONAUER ELECTRICAL RESISTANCE INSTRUMENT Filed Feia. 12, 192 5 Patented Nov. 2, 1926.

UNITED STATES,

IRANK C. KRONAUER, OF PATERSON NEW JERSEY.

ELECTRICAL RESISTANCE INSTRUMENT.

Application filed February My invention relates to electrical resistance instruments of the kind used in radlo and similar electric circuits, and the object of my invention is toprovide a variable resistanceinstrument that admits of easy and accurate control and adjustment of high resistances.

I accomplish this object by means of the instrument described in this specification and illustrated in the attached drawing that forms a part of this specification. In this drawing, Fig. 1 shows a view of the instrument, disclosing the variable resistance fea-' tures and itsconstruction; Figure '2 is a cross section taken. along the line 22 of Fig. 1. .Figure 3 is a longitudinal section of the connecting sleeves S and S of Fig. 1, showing the method of inserting the container tubes T and T. Figure 4 is a longitudinal section of a fragment of the container tube T and shows a conductor pin Y sealed into the tube T. Similar letters refer to similar parts throughout the several views.

The container tubes, T and T, each forming an arc of a circle, are constructed of any good insulating material suitable for thepurpose, preferably glass. These tubes are joined by the metallic sleeves S and S. The depressed ring if of the sleeves S and S prevent the tubes T and T from making contact, andprovide two metallic segments in the interior of the tubular container ring, S, T, S, T. This container ring is attached to the insulating support'B "by the clips C and C. These clips aflord electric contact between the sleeves S and S and the binding posts P and P respectively. The support 13 is secured to turn with the shaft F in the bearing K which is inserted in the su porting panel D. The usual type of ra io instrument dial I is attached to the shaft F to facilitate operation of the instrument.

During the process of manufacture a qllxlantity of mercury, M, is introduced into t e container tube T T. This mercury occupies about one third of the volume content of the entire container ring. The container ring is then filled very nearly full with a suitable fluid resistance R,'the specific gravity of which is less than that of the mercury. The tube is then sealed to feign a 'cd'n'tinuoua ring as illustrated. The mercury M falls to ,the lower section of the container ring, while the fluid resistanceB, which fol-high resistances is preferably some form of refined mineral 011, of mnteble'and conduc- 12, 1925. Serial No. 8,852.

tivity, rises above the level of the mercury, as illustrated in the drawing. Electrical contact with the mercury M and the fluid R is maintained through the sleeves S and S respectively, and so through the binding posts P and P that form the electrical terminals of the instrument.

lVhile S and'S are, with respect to the level L of the-mercury M, in the position shown in solid lines in Fig- 1, the electrical resistance of the instrument is maximum, since the conductivity of the fluid, R is very much smaller than that of themercurv M. If we nowrotate the container tube and its support B on the shaft F, in the direction of the arrow V to the position shown in dotted lines in Fig. 1, the resistance of the circuit P S R M S P has decreased, since the distance from the'contact S to the level L of the mercury M has decreased, while S continues to make contact with the mercury .M. In other words the resistance of the in:

strument has been reduced by this setting. e can continue to rotate the ring container and its support in the direction of the arrow W until the contact S very nearly touches the mercury M. At this point while still retaining 'the fluid R in the circuit, the minimum resistance of the circuit P RM P will, be found.

- It -will be seen that in this manner a smooth variation in resistance can .be obtained by a partial rotation of the instrument about its axis, provided that the instrument is mounted with the tubular ring view Fig. 4, can be sealed into or through the tube. T, substituting for the contact S or S. The face X of the dial I has suitable graduations common to radio instrument dials. The sleeves S and S can, if desired be constructed of other conducting material than metal. Carbon can be used for this pur ose. v

e change in resistance in the vglyh'pe of inhereinbefore described not deple in a convenient and useful manner, but

crease directly in proportion to a decrease in the distance between S and L. This is due to the conductivity of the fluid R between S and L, Fig. 1. When using mercury for the fluid M and a high resistance fluid for R, the resistance of the mercury column can be neglected for practical purposes; The

divided circuit resistance for any position of S and S can be computed for the circuit of resistances in parallel, S L S, and S L S, in the well known manner.

If it is desirable to have the resistance of the instrument vary in proportion to the distance between S and the surface L, mercury is preferably used for the fluid M and a high resistance fluid for R. Then, during the process of manufacture, the level of R' is raisedonly to theline 1 1', Fig. 1. When so constructed the range of the instrument will be limited to a movement of contact S between the radial lines AA' Fig. 1.

It will be seen from the foregoing that the principle of my invention consists essentially of the use, in a circuit, of two fluid conductors of unlike conductivity and specific gravity, that at their surfaces of contact form closed points in the circuit, together with means for varying the electrical lengths of the said fluids in the circuit. A plurality of fluids may be substituted for the fluid R, if desired/ The instrument illustrated and described-- in these specifications embodies this princivhis instrument can be constructed differently without departing from the spirit of my invention, and I do not wish to limit the scope of my invention to the details and features of construction shown and described in these specifications.

I claim as new and desire to secure by Letters Patent the following? 1. In a variable resistance instrument, the combination of two fluid conductors that differ in conductivity and specific gravity, means for making electric contact with each of the said fluids separately, and means for varying the positions of the said contacts with respect to the relative positions of the said fluid conductors.

2. In a variable resistance instrument, the combination of two fluid conductors that differ in specific gravity and conductivity,

means for maintaining each of g the said fluids as individual sections of an electric circuit of which the said instrument forms a part, means for keeping'a portion of the surface of each of the said fluids in contact with a portion of the surface of the other contact with each of the said fluid conductors separately.

4. In a variable resistance instrument,the combination of a plurality of fluid conductors diifering from onea'nother in conduce tivity and specific gravity, an insulating container in'closing the said fluid conductors,

.means for making separate electric contacts between the said fluid conductors and a circuit external to the said insulating container, and means for varying the positions of the said contacts with respect to the relative positions the said fluid conductors have to one another. 4

' FRANK G. KRONAUER. 

